Reforestation is a necessary, and in several countries by law prescribed method to achieve a sustainable forestry. One method is to leave selected seed-trees on the clear-cutting, another to plant seedlings after different kinds of soil preparation. The methods can be used in combination. Planting of seedlings is used to assure that a certain plant density is achieved on the regeneration area.
Many dangers, e.g. drought and attacks from wild animals and insects, threaten the development of a managed forest stand. A high rate of survival of the plants means reduced costs for the reforestation and increased future income.
Attacks from insects are very costly for the forest industry. Treatment of seedlings with insecticide (permethrin) will not be allowed in the European Union in the future. In spite of the fact that a ban has been proposed for several years, permethrin is still allowed for use, since the economic consequences of a ban has been regarded as insurmountable for the forest industry.
Coniferous seedlings are often treated with permethrin in the plant nursery before sale. The treatment of the plant with permethrin is often repeated in the field the following year. The treatment with permethrin is thus connected with increased costs in addition to the initial costs.
A great number of methods for reducing plant damage without using permethrin have been invented and developed. These methods have been assessed in both field tests and laboratory examinations (Lindström et al 1986, Eidmann & Sydow 1989, Eidmann et al. 1996, Hagner & Jonsson 1995, Hofsten et al. 1999,).